In general, inkjet printers include at least one printhead having a plurality of inkjets for ejecting drops of ink toward an ink receiving surface. In some printheads, the plurality of inkjets is implemented by a stack of laminated sheets or plates, commonly referred to as an inkjet stack. As an example, printhead 22 shown in FIG. 3 includes an inkjet stack 40 having an aperture plate 46 that includes apertures 44 through which drops of ink are ejected by the inkjets. The inkjet stack also includes ink passages or channels 42 that deliver ink to the inkjets. The ink passages 42 of the inkjet stack supply channels receive ink from an on-board reservoir 50 of the printhead via one or more ink supply ports 52.
The ink receiving surface may comprise recording media, such as paper, or an intermediate imaging member, such as a rotating drum or belt. During operation, the ink receiving surface is moved past the printheads in a direction referred to herein as the process direction. The inkjets of the printheads are arrayed in a direction perpendicular to the process direction, also referred to herein as the cross-process direction. In some previously known printers, the individual printheads used in the printer are narrower than the width of the ink receiving surface in the cross-process direction. To enable full width printing in these printers, multiple printheads are arranged across the width of the ink receiving surface. Each printhead, however, requires a separate electrical and ink supply connection. Using multiple printheads to enable full width printing may therefore increase the cost and/or complexity of the printer.
As an alternative to using multiple printheads to enable full width printing, a single printhead that is wide enough to extend across the width of the ink receiving surface may be used. An example of a full width printhead is depicted in FIG. 4. In order to supply ink to all of the inkjets of the inkjet stack 40 in a timely manner, the inkjet stack is connected to the reservoir 50 using multiple ports 52. For example, in FIG. 4, two supply ports 52 are used to connect the on-board reservoir 50 to the supply channels (not shown in FIG. 4) of the inkjet stack 40 with one supply port 50 being located near each lateral end 56, 58 of the reservoir. A single full width printhead requires fewer electrical and ink supply connections than multiple printheads combined into an array. Therefore, using wider printheads may decrease the cost and/or the complexity of a printer.
Wider printheads, however, are more sensitive to the effects of tilting than narrower printheads. For example, when a reservoir is not tilted, as depicted in FIG. 4, the distance between the bottom surface 60 of the reservoir 50 and the top surface 54 of the ink in the reservoir 50 is the same across the width of the reservoir. When the reservoir is tilted as depicted in FIG. 5, one end 58 of the reservoir dips lower than the other end 56. Consequently, as ink volume shifts toward the lower end of the reservoir, the distance H2 between the bottom surface of the reservoir and the ink level in the lower end 58 of the reservoir is increased (i.e., H2>H), and the distance H1 between the bottom surface 60 of the reservoir and the ink level in the higher end 56 of the reservoir is decreased (i.e., H1<H).
Depending on the magnitude of tilt, the decreased ink height H1, where H1 is less than H, in the higher end 56 of the tilted reservoir may cause the ink port 52 in that end 56 of the reservoir to be located partially or fully above the top surface 54 of the ink, as depicted in FIG. 5. Consequently, the ink port 52 may not be able to adequately supply ink to that end of the inkjet stack. In addition, as is known in the art, changes in ink height in the reservoir may cause a corresponding change in the pressure head on the ink at the apertures 44 in the aperture plate 46. The changes in ink height caused by tilt may therefore result in unexpected pressure variations in the printhead that may result in inconsistent drop formation by the inkjets of the inkjet stack.